1. Field of the Invention
The present invention relates in general to an optical communication of information and more particularly to a system and a method for optically communicating information between a display and a camera that is observing the display.
2. Related Art
Optical communication between an image source (such as a display) and an image detector (such as a camera) is desirable and has several applications. By way of example, if a computer network contains several devices and sensors within a large physical space, the addition of a new device (such as a display or a camera) could be greatly simplified if the display and the camera were in optical communication. The display and camera would simply establish an optical communication link and transmit information (such as a network address). In this manner a new device could be connected to the computer network automatically and without human intervention.
Unfortunately, there are few techniques currently available that permit optical communication between a display and a camera. There are some techniques, however, that allow optical communication between other types of devices. For example, one technique facilitates data transmission between a display and a watch having a photosensor. This technique permits data to be downloaded from the computer (via the display) to the watch memory. One disadvantage, however, of this technique is that a large degree of human intervention is required to facilitate the download. In particular, the user must hold the watch up to the display for the duration of the download, which can be tiring for the user and lead to inaccurate and incomplete data transmission. In addition, this technique and others have the disadvantage of not being able to automatically determine the spatial location (or pose) of the display relative to the camera observing the display. Knowledge of the display pose is important because when the pose is known the system is able to include the display and camera in any physically-based user interface. For example, if the system wants to send a user a visual message, it is necessary to select a display that the user can actually see. If the cameras (or appropriate hardware) are used to track the location of the user, then the physical relationship between user and camera can be determined. By repeating this process for all displays, it is possible to select the display that is in the most advantageous location for interacting with the user.
Accordingly, there exists a need for a system and method for optically communicating information between a display and a camera that is automatic and does not require any human intervention. This system and method would allow a variety of information to be transmitted between the display and camera to facilitate, for example, automatic connection of a new device to a computer network. In addition, this system and method for optically communicating information would enable a pose of the display to be determined relative to the camera. Whatever the merits of the above-mentioned systems and methods, they do not achieve the benefits of the present invention.
To overcome the limitations in the prior art as described above and other limitations that will become apparent upon reading and understanding the present specification, the present invention includes a system and a method for optically communicating information between a display and a camera that is observing the display. In general, the transmission of information is unidirectional in a direction from the display to the camera. The display of the present invention includes any device (such as a cathode ray tube (CRT) monitor) capable of transmitting information via communication symbols (such as characters, patterns, images, etc.). The display transmits information to the camera that is observing the display by using the communication symbols and displaying the symbols on the display. Information (such as a network address) may be transmitted to the camera without any prior shared knowledge between the display or the camera. Using either a stereo camera or a monocular camera, the present invention also is capable of determining a spatial location of the display (relative to a camera observing the display) by observing a pattern presented on the display and using well-known correlation techniques.
In general, the method of the present invention includes locating a display ready to communicate information, using the display to communicate communication symbols to a camera that is observing the display in order to xe2x80x9cteachxe2x80x9d the camera, and transmitting information from the display to the camera using the communication symbols. In addition, a preferred embodiment includes having the display notify the camera that the display is ready to transmit information by displaying a prominent pattern. This informs the camera that a certain display will begin transmitting information. Next, the communication symbols between the display and the camera are defined by having the display present each of the communication symbols to the camera. This presentation of the communication symbols is done in sequence, such that the camera assigns a definition to each of the communication symbols. The display then optically transmits the information using the communication symbols and the previously-obtained definition of the communication symbols is used by the camera to decode the information sent by the display. In this manner the display can optically transmit any type of information to the camera. In addition, the display can display a localization pattern such that the camera can determine the spatial location of the display relative to the camera.
Moreover, the present invention also includes stabilizing video images of the display in the event that the display is a cathode ray tube (CRT) design. More specifically, the present invention includes an aggregation technique that obtains a series of camera images and produces a stabilized aggregated image to minimize flicker caused by the display being refreshed. In addition, the present invention includes a method for using either a stereo camera or a monocular camera to determine a pose of the display (relative to the cameras). In a preferred embodiment, the technique uses a stereo camera to measure pose and includes using a random localization pattern displayed on the screen to be observed by the stereo camera in order to maximize the probability of a strong correlation for each pixel. In an alternate embodiment, a monocular camera is used to measure pose by determining camera calibration parameters, detecting three or more points on the display, determining the relative positions on a plane of these points in physical (or real) units and computing the display pose relative to the camera using correlation techniques well-known to those of ordinary skill in the art. The present invention also includes a system for optically communicating information between a display and a camera using the above-described method.
Other aspects and advantages of the present invention as well as a more complete understanding thereof will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. Moreover, it is intended that the scope of the invention be limited by the claims and not by the preceding summary or the following detailed description.